int DIP_VALUE = 5;
int pixel = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, DIP_VALUE, getResources().getDisplayMetrics());

//or simply
float pixels = getResources().getDimensionPixelSize(DIP_VALUE);

mTextView.setTextSize(pixels);

public static float getDipFromPixels(float px) {
        return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_PX, px, Resources.getSystem().getDisplayMetrics());
}

public static float getPixelsFromDip(float dip) {
       return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dip, Resources.getSystem().getDisplayMetrics());
}